The n-3 polyunsaturated fatty acids (PUFA) have been proposed as potential treatments for human heart failure. The cardioprotective effects of n-3 PUFA are supported by extensive cell culture, animal and human studies. Animal studies with n-3 PUFA have shown marked improvements in many independent risk factors for heart failure, including obesity, type II diabetes, insulin resistance, hypertension and inflammation. However, the evidence from observational studies, randomised controlled trials and meta-analyses that these benefits on risk factors lead to improvements in the symptoms of heart failure in patients is much less convincing. Further, most studies have used marine n-3 PUFA; the role of the plant-derived PUFA, α-linolenic acid (ALA), is even less clear. This discontinuity of scientific evidence from animal to human studies suggests that future studies should focus on defining the optimal dosage range and the efficacy of n-3 PUFA compared to standard treatments using standardised study designs. Further studies on ALA would seem justified.